JPS61161191A - Treatment of heavy metal ion-containing solution - Google Patents

Abstract

PURPOSE:To remove enough heavy metal ions to make a heavy metal ioncontaining solution harmless for a comparatively short period of time by performing each addition process of a chelating agent, activated charcoal and flocculating agent to a heavy metal ion-containing solution. CONSTITUTION:0.9-1.2 equivalent weight of chelating agent based on heavy metal ions present is added to said solution. Next, in the weight ratio, about 250-400g activated charcoal is added to 1 ton original water, and further about 0.05% concentration of solution contg. about 1-3g flocculating agent is added to 1 ton original water. As a result, the heavy metal ions can be removed almost completely up to an analytical limit and further the amt. of generated sludge is also small. Also, the sampling test at each step is not necessary.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for treating a liquid containing heavy metal ions discharged from a laboratory or factory.

[Prior art]

Various compounds are used in laboratories and factories, and wastewater also contains these compounds or their ions. Many of them are harmful, and discarding them directly contributes to environmental pollution. In particular, many heavy metal ions are harmful to the human body. For example, PB accumulates mainly in the bones and causes various disorders, while As causes neurological disorders, vascular disorders, etc., and has a large influence on living bodies. Therefore, it is necessary to detoxify it before disposal.

Conventional detoxification treatment methods include the heavy metal scavenger method,
Neutralization precipitation method, sodium sulfide method, chelate other agent method, chelate resin method, etc. have been proposed and have been carried out singly or in combination.

The heavy metal collection method is a method in which heavy metal ions are reacted with a heavy metal collection agent to form a water-insoluble complex, and the complex is separated using a flocculant. Although this method has the advantage of being relatively inexpensive, it is difficult to complex all of the heavy metal ions, and an excess of heavy metal scavenger must be used to form a sufficient complex. Residue of heavy metal scavengers poses a new problem.

The neutralization coagulation method is a method in which the pH of wastewater is made alkaline with caustic soda or the like, heavy metal ions are converted into water-insoluble hydroxides, and the wastewater is separated by precipitation using a flocculant. Although this method has the advantage of being inexpensive, the removal rate of heavy metal ions is not satisfactory.

The sodium sulfide method reacts heavy metal ions with sodium sulfide,
This method produces water-insoluble sulfide and separates it by precipitation using a flocculant. Although this method is also relatively inexpensive, it poses problems in that harmful hydrogen sulfide is generated when heavy metal ions and sodium sulfide are reacted, and that sodium sulfide remains.

The chelating agent method is a method in which a chelate compound of heavy metal ions is formed and separated using a chelating agent. In the chelating inhibitor method, all heavy metal ions are theoretically converted into chelate compounds by using one equivalent of the other chelating agent for one equivalent of heavy metal ions, but in reality, this does not proceed as planned. Especially in the case of industrial wastewater, since a large amount of wastewater is treated, the chelation rate remains at about 80%. Chelation rate 100
%, a large excess of chelating agent must be used, especially in continuous processing systems.

Even if the chelating agent is stirred during the reaction to increase the chelation rate, a large excess of chelating agent is still required. If the 0 batch processing method is adopted, the chelation rate can be increased more than the continuous treatment method, but it is not enough. Chelation takes a long time and still requires an excess of chelating agent. If an excessive amount of chelating agent is used, the chelating agent may remain, the quality of the effluent water may deteriorate, etc. Since a large amount of chelating agent is used, there are further problems of high treatment costs.

The chelate resin method is a method of selectively adsorbing heavy metal ions by bringing a heavy metal ion into contact with a chelate resin and forming a chelate bond between the functional group of the chelate resin and the heavy metal ion. According to the chelate resin method, chelation proceeds almost according to theory, and heavy metal ions are removed at extremely low concentrations (0.05
It is possible to remove up to PP■ or less. However, since chelate resins are expensive, they are generally recycled and used, and treatment of the eluent containing heavy metal ions involves similar problems.

1-As mentioned above, among the conventional methods, only the chelate resin method can remove heavy metals to a low concentration. however,
As already mentioned, the chelate resin method cannot be a final solution.

Furthermore, no matter which method is adopted, conventional methods require sampling and analysis for process checking, which poses problems such as the time and cost involved, and the inability to proceed to the next process until the results are available. Ta.

[Problem that the invention seeks to solve]

The object of the present invention is to provide a heavy metal ion treatment method that can remove enough heavy metal ions to render water containing heavy metal ions harmless in a relatively short period of time.

A further object of the present invention is to provide a heavy metal ion processing method that does not require sequential sampling inspection at each step.

[Means for solving problems]

The above object of the present invention is achieved by the following processing method.

That is, a method for treating a liquid containing heavy metal ions and a method for chelating the liquid containing heavy metal ions, which comprises the steps of adding at least a chelating agent, adding activated carbon, and adding a flocculant to the liquid containing heavy metal ions. The process consists of a step of adding a chemical agent, a step of adding activated carbon, and an upper step of adding a flocculant, and the removal rate of heavy metal ions is kept below a predetermined value based on the changes in hydrogen ion concentration and redox potential in each step. This is a method for treating a liquid containing heavy metal ions.

Preferably, the step of adding a flocculant comprises a step of adding a non-Ia flocculant and a step of adding an organic polymer flocculant.

Heavy metal ions that can be treated with this method are
i′If ability contained in laboratory or listed wastewater +11
It is nJ ability to apply it to something in a balanced way. Especially H
g24, Gd", Cd", Cd'◆, Cu",
Suitable for processing Pb7", Zn", As", etc.6
It is desirable that the treatment method of the wood invention be a batch treatment method.

A flow sheet of the treatment method of the present invention is shown in FIG. 1, and will be explained according to the flow sheet.

The first step of the treatment method of the present invention is to clean one heavy metal ion.
1. In the compound production stage, it is necessary to adjust the pH to an optimum level before adding the chelating agent. The pH may be adjusted using a pH adjusting agent such as sodium hydroxide or hydrochloric acid, or by mixing an acidic waste liquid and an alkaline waste liquid.

An appropriate chelating agent is selected depending on the type of heavy metal ion to be treated. Chelating agents may be low molecular weight compounds such as ethylenediamine, EDTA, sodium gluconate, Rochelle's salt, potassium pyrophosphate, triethanolamine, and sodium hypophosphite;
can react with most heavy metal ions to form, precipitate, and aggregate insoluble m, and there is no need to worry about secondary contamination with drugs, and it is not affected by coexisting salts. Particularly preferred are chelating agents. As a chelating agent for a polymer compound, for example, Epofloc L-1
(Miyoshi Oil Co., Ltd.), Sumifloc HM 2000, etc. can be used.

The addition of the chelating agent varies depending on the chelating agent and the blocking agent, but it cannot be generalized, but the amount of addition of the heavy metal ion is 0.8 to 1.
2 equivalents are preferred.

The second step is a step of removing residual metal ions that did not become a chelate compound in the first step. This step is carried out by injecting powdered activated carbon. Powdered activated carbon is injected after the first stage reaction has sufficiently progressed.

In this process, by adsorbing the chelating agent and heavy metal ions on the surface of activated carbon, what remains unreacted in the solution can be efficiently reacted, and the generation of chelate compounds of heavy metal ions can be completed. can. The amount of activated carbon added is approximately 250 to 400g per raw water.
is appropriate. It is desirable to stir the solution to prevent activated carbon from precipitating and to disperse it homogeneously in the solution.Activated carbon also adsorbs, decolorizes, and deodorizes residual substances other than single heavy metal ions, and also serves as a nucleus for coagulation and coprecipitation. Now.

The third stage is a step in which the chelate compounds produced in the first stage and the second stage are flocculated and separated by adding a flocculant. As a flocculant, Feα3 or (Fe2(OH)n(SO4)3)m,
CFe(OH)2)'-.

(Fe(O)l) ) '-, iron polymers, etc.
Poly 11! Aluminum chloride or the like can be used.

These flocculants coagulate chelate compounds, insolubilize unreacted chelating agents, neutralize the load of suspended fine particles in water, and coagulate. It has characteristics such as rapid floc formation and rapid sedimentation, making it suitable.

As the iron polymer, commercially available polyiron (Nippon Steel Mining ■) is suitably used. Polymer flocculants such as polyiron reduce the volume of the generated sludge and increase the sedimentation rate without having a negative effect on the effectiveness of the main treatment process. The flocculant.

One type may be used or two or more types may be used in combination. For example, it may be possible to first coagulate and sediment using an inorganic flocculant, and then to coagulate and sediment using an organic flocculant. As the organic flocculant used in combination with the inorganic flocculant, a polymer compound is also suitable, for example.

Sunfloc AH-210P, 2QOP, 150P
(Sanyo Kasei product), Orflock 0A-5, Clifflock 0A-385°, Sumiflock FA-10, and other commercially available products can be used. The amount of the flocculant to be added varies depending on the flocculant, but in the case of a polymer flocculant, it is appropriate to add about 1 to 3 g to the raw water It as a solution with a concentration of about 0.05%.

A neutralization step may be provided during the third step or after all steps are completed.The neutralization step does not need to be provided after all steps are completed if the treated waste liquid is approximately neutral.
If the treated waste liquid is alkaline or acidic, it is desirable to neutralize it after all steps are completed. When the aggregation step is divided into two stages as described above, the neutralization step may be performed in the middle. As the neutralizing agent, sodium hydroxide, hydrochloric acid, sulfuric acid, lime, etc. can be used.

Furthermore, in order to completely deodorize the waste liquid, a small amount of hydrogen peroxide may be added at the end.

The method of controlling the heavy metal ion removal rate to a predetermined value or less based on changes in hydrogen ion concentration (pH) and redox potential ORP is suitable for the treatment of industrial wastewater where the type and concentration of heavy metal ions contained are constant. ing.

If there is no difference between the standard pattern diagram prepared in advance and the drawn pattern diagram, it can be said that the removal rate of heavy metal ions is below the predetermined value. If a difference is recognized, it is a batch processing method, and the same processing can be repeated once again.

An example of a standard pattern diagram is shown in FIG. 2. The standard pattern diagram shown in FIG. 2 is for an ion exchange eluent of wastewater from a glass polishing factory.

[Example] In order to explain the present invention more specifically, Examples are shown below.

Example Optical glass wastewater was treated with an ion exchange resin, and the saturated ion exchange resin was treated with T during the optical glass closed system process.
The ions were eluted by passing through the filtered water.

The acidic eluent and the alkaline eluent were mixed to a pH of 7 to obtain treated raw water. This treated raw water contains Pb2
``, As'' are included at 10 ppm and 2 ppm, respectively. 2,800 cc of Epofloc L-1 (Miyoshi Oil ■) as a chelating agent was gradually injected into 7 tons of treated raw water over 6 minutes, and the mixture was allowed to react for 20 minutes. Next activated carbon 7
After injecting 0 sentence for 3 minutes and reacting for 20 minutes.

As an inorganic coagulant, polyiron (Nichisen Mining ■) was injected for 6 minutes and then allowed to react for 1 minute. Since polyiron is strongly acidic, NaOH was added to neutralize it. After neutralization, Sunfloc AH-200P (manufactured by Sanyo Chemical Co., Ltd.) was added as a polymer flocculant for 28 minutes to grow flocs. After the injection of Epofrost, the operation was performed while stirring with a stirrer. When the flocs have grown sufficiently, stop the stirrer, and
After standing for ~3 hours to allow the flocs to settle, the sludge was separated.

The pH and ORP patterns measured by the pH meter and ORP meter are as shown in FIG. 3, and match the standard pattern diagram prepared in advance (FIG. 2), confirming that the treatment has been completed. For confirmation, the final concentrations of Pb2" and As" were adjusted to (quantification method: JISKO102.54.2).
When measured, Pb2+ was below the detection sensitivity, and As3+ was 0. When 800.00 mouths of the supernatant after separating the sludge was measured, it was confirmed that it was purified to t, app, and 3 ppm, respectively. Since the supernatant remained slightly colored and had a slight odor, a small amount of hydrogen peroxide was added to bleach and deodorize it, and after confirming that there was no residual H2O2, it was discharged.

〔Effect of the invention〕

According to the uninvented treatment method, heavy metal ions can be almost completely removed to near the analytical limit, and the amount of sludge generated is also small. Furthermore, sampling inspection at each stage is not necessary.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet of the treatment method of the present invention. FIG. 2 is a standard pattern diagram of fluctuations in hydrogen ion concentration and redox potential in the treatment method of the present invention, and FIG. 3 is a diagram of their fluctuation patterns in an example of the present invention. : Suimine Torafu ○RP

Claims (1)

[Scope of Claims] 1) A method for treating a heavy metal ion-containing liquid, comprising the steps of: adding at least a chelating agent, activated carbon, and a flocculant to the heavy metal ion-containing liquid. 2) The method for treating a heavy metal ion-containing liquid according to claim 1, wherein the step of adding the flocculant comprises a step of adding an inorganic flocculant and a step of adding an organic polymer flocculant. 3) Consists of at least a step of adding a chelating agent, a step of adding activated carbon, and a step of adding a flocculant to the heavy metal ion-containing liquid, and is based on changes in hydrogen ion concentration and redox potential in each step. 2. The method for treating a heavy metal ion-containing liquid according to claim 1, wherein the treatment is carried out so that the ion removal rate is equal to or less than a predetermined value.